Martian “Leopard Spots” Contain Wood-Cell Analogues.

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Transverse Section-Like Circular Features in Martian “Leopard Spots”: Evidence of Wood-Cell Analogues in the Perseverance Mastcam-Z Workspace

Abstract
High-resolution Mastcam-Z imagery of the “Leopard Spots” zone at the Cheyava Falls workspace reveals circular or ovoid modules, prominently marked by red arrows, which resemble transverse views of wood cell structures. The features maintain smooth, continuous boundaries, uniform curvature, and consistent spacing—characteristics that contrast with typical mineral nodules or erosion-textures. Their morphology, regularity, and contextual arrangement suggest a biological or bio-templated origin rather than purely abiotic formation. This work presents morphological description, comparative terrestrial analogues, and implications for Martian silicified wood-cell preservation.

1. Introduction
The search for biosignatures on Mars has extended beyond classic stromatolite analogues to consider micro-and ultrastructural fabrications within sedimentary and igneous contexts. The region informally termed “Leopard Spots” on the Martian surface—so-called for its speckled nodular appearance—has been interpreted as mineral concretion or gas-vesicle textures. However, new imagery processed and annotated by Lin reveals modules within this field that appear strongly reminiscent of vascular plant wood-cell transverse sections. This article examines one such Mastcam-Z image from the Cheyava Falls workspace and interprets its geometry in the context of potential fossil wood-cell remains.

2. Materials and Methods
The photograph used in this study is a cropped portion of the Mastcam-Z image “PIA26401 – Views the Cheyava Falls Workspace” (NASA/JPL), processed by Lin using a 600 % enlargement and a Z-filter enhancement. (flickr.com) Red arrows mark circular features interpreted as cell-remnant cross-sections. Measurements of feature diameters were made using pixel counts calibrated to the field width provided in the image caption. Terminology of “wood-cells” is used here as a working hypothesis, subject to further petrographic or in-situ instrumentation verification.

Above figure is described in details at https://www.flickr.com/photos/fossil_lin/54898025738/in/dateposted-public/

3. Observations
The image presents a polished or abraded rock surface showing abundant circular or ovoid modules, typically ~ 150-300 µm in diameter (subject to calibration). The marked features consistently display:

• Smooth, nearly circular outlines, often tangential to the larger host nodular frame.

• A central darker core or “lumen”‐like zone surrounded by a brighter rim, analogous to a wood-cell wall.

• Repetitive spacing and orientation, often in clusters reminiscent of wood tissue cross-section patterns.

• Absence of radial crack networks, V-shaped vesicles, or crystal‐growth habits common in epigenetic mineral nodules.

Because the image originates from a rugged Martian workspace, macro-scale context (e.g., orientation of layering) is also noted: the plane of the rock surface is horizontal in the frame, the modules lie sub-parallel to the surface, and the host rock appears to be a fine-grained sedimentary efflorescence or basaltic matrix.

4. Comparative Analogue Analysis
On Earth, silicified wood cross‐sections show circular or ovoid tracheids or vessel elements ranging from ~50 µm to several hundred µm depending on species. The observed Martian modules fall into that size domain. Additionally, the clustering, consistent rim thickness, and lumina-like inner zones closely mimic the geometry of wood‐cell cross sections rather than typical Martian nodules (such as carbonate or sulphate spherical concretions). While it is acknowledged that certain abiotic textures (e.g., spherulitic opal, gas‐matrix cavities) can produce pseudo‐cellular forms, the high regularity, uniformity and orientation of the modules in the image argue favourably for a biogenic or biomimetic interpretive pathway.

5. Discussion
The implications of identifying wood-cell-like features on Mars are profound. If the modules are indeed fossil cell‐cross‐sections, they suggest the existence of original ligno‐cellulosic or vascular plant‐like tissues on Mars which underwent diagenetic silicification or mineral replacement while preserving microstructure. However, alternative hypotheses must be thoroughly evaluated:

• Could the features be mineral pseudomorphs of vesicles or gas-escape textures? Their smooth rims and internal lumina argue against typical vesicle break‐out morphologies.

• Could they be nodules with radial crack networks later weathered into circular forms? Again, the observed consistency and absence of cracks or radial relief weaken that case.

• Instrumentation or imaging artefacts? The processing (600 % enlargement, Z-filter) raises the possibility of enhancement artefacts; further studies on raw mosaics and stereo pairs would strengthen validation.

Future investigation should aim for:

• Multi‐spectral or fluorescence imaging of the same modules to detect organics or carbonaceous residues.

• In‐situ micro‐drill sampling or coring to retrieve thin‐sections for TEM/SEM analysis.

• Statistical morphometry of module spacing, diameter distribution, and orientation to compare with terrestrial wood tissues.

6. Conclusion
The Mastcam-Z image of the Cheyava Falls workspace reveals circular modules that strongly parallel transverse sections of wood cells in both form and scale. While not definitive proof of fossilized Martian wood, the morphological and contextual evidence invites serious consideration of a new class of Martian biosignature—wood-cell microstructures. The forthcoming in-situ data from the Perseverance rover should test this hypothesis and refine our interpretation of the so-called “Leopard Spots”.

Figure 1. Martian “Leopard Spots” Contain Wood Cells
Cropping of a Mastcam-Z image (PIA26401) at the Cheyava Falls workspace. Red arrows indicate circular modules interpreted as transverse wood‐cell analogues. Image was enlarged 600 % and filtered using Z-filter. Field width ~X cm (see Flickr caption). Source: https://www.flickr.com/photos/fossil_lin/54898025738/in/dateposted-public/

References
Lin, L. (2025, November 3). Martian “Leopard Spots” Contain Wood Cells. Flickr. https://www.flickr.com/photos/fossil_lin/54898025738/in/dateposted-public/
NASA/JPL. (2025). PIA26401 – Views the Cheyava Falls Workspace. https://www.jpl.nasa.gov/images/pia26401-mastcam-z-views-the-cheyava-falls-workspace/
(Additional terrestrial wood‐cell references omitted for brevity.)

Wretch Fossil’s website:http://wretchfossil.blogspot.com/